[NEW] Support node discovery in standalone (cluster mode disabled)

[asafpamzn]

The problem/use-case that the feature addresses

In cluster mode clusters the clients gets the topology using one of the cluster commands. The ask is to create a similar command for standalone clusters.

It will simplify the usage for users that works in standalone but have dynamic number of replicas. That is, during the life time of the cluster they delete and adds replicas

Description of the feature

Implement new command to get the topology of standalone cluster.

Alternatives you've considered

Migrate to cluster mode enable, but it cannot cover all use cases.

Additional information

Any additional information that is relevant to the feature request.

[hpatro]

It would be nice to capture what are the steps used by the clients currently in standalone setup? Is the information currently built via INFO REPLICATION on the primary ? And what are the shortcomings with it?

[asafpor]

Usually clients just get the endpoints as parameters and do not discover the nodes.

If there is an option to get via replication info we can guide client maintainer to use it. Is the info replication avaliable in elasticache and other valkey providers?

[hpatro]

Thought about it a bit more, I guess what is missing at this point is passing around the hostname information in standalone mode. In cluster mode, we use the cluster bus to gossip that information. if the replica setup was performed via REPLICAOF ip port, it might not be enough information for client to use and connect to.

[asafpamzn]

@hpatro. "Thought about it a bit more,"
is (It == my request for "cluster nodes" in standalone.)
Or (it == INFO REPLICATION)

?

[hpatro]

@asafpamzn around your request and what is lacking.

"I guess what is missing at this point is passing around the hostname information in standalone mode. In cluster mode, we use the cluster bus to gossip that information. if the replica setup was performed via REPLICAOF ip port, it might not be enough information for client to use and connect to."

[asafpor]

@madolson , is that something that we can prioritize.
On one hand we want users to move to CME.
On the other hand. We need this feature in order to support read from replica at CMD. It will allow to client to hold all replicas endpoints.

I think that it is a quick win. See
valkey-io/valkey-glide#3091